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Heartworms? What Are They and What To Do About Them

What are Heartworms?

Heartworms, or Dirofilaria immitis, are a parasite that live in the arteries of animals like dogs and sometimes cats. They are spread by mosquitoes biting and transferring early life stages of the parasite from animal to animal. Any area in the US that has mosquitoes can have a population of heartworms as well.

Prevention vs Treatment

Prevention is the most effective way to deal with heartworms as treatment is a costly and lengthy procedure. Infected animals are required to undergo a regimen of expensive medications and are confined to cage rest for multiple months. There is no effective treatment for cats, which makes prevention even more important.

Heartworm preventatives come in oral, topical and injectable forms. We carry Heartgard Plus, a once a month oral preventative in our clinic. The American Heartworm Association recommends heartworm prevention year round, and not just during the warmer months when mosquitos are active. While Wyoming is not really a hotspot for positive heartworm cases, we definitely recommend prevention if you and your dog are traveling to warmer states, or states with active heartworm populations.

How Do I Start my Animal on Heartworm Preventative?

Your pet requires a blood test to screen for heartworms before starting a heartworm preventative. This makes sure that they are negative, as giving a preventative when there are active adult heartworms could make your pet seriously sick, or even kill them. Once on a preventative, the American Heartworm Association recommends a blood test once a year to ensure no active parasites are present, even if your pet is on a preventative year round.

We will not prescribe your animal a heartworm preventative without a history of being consistently on the preventative year round or a negative blood test. This includes in person or through our online pharmacy. After your appointment we can prescribe other heartworm medications aside from the Heartgard Plus through our online pharmacy, which you can find linked in the menu bar above. We do not prescribe medications through Chewy or other online pharmacies at this time.

Please feel free to call the clinic at 307-436-8313 if you would like to start your pet on heartworm prevention, or have any questions!

Until next time, I hope you stay healthy and parasite free!



Noack S, Harrington J, Carithers DS, Kaminsky R, Selzer PM. Heartworm disease - Overview, intervention, and industry perspective. Int J Parasitol Drugs Drug Resist. 2021 Aug;16:65-89. doi: 10.1016/j.ijpddr.2021.03.004. Epub 2021 Apr 27. PMID: 34030109; PMCID: PMC8163879.

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